The present invention relates to a transmission device for knife changing mechanism of a machine center wherein the transmission distance between the cam and the main shaft is shortened and a gap between the control shaft can be adjusted.
A conventional transmission device 60 for knife changing mechanism of a machine center is shown in FIG. 7 and generally includes a motor which drives a belt 62 with its output shaft 61 and a gear shaft 63 is rotated by the belt 62. A worm gear 631 is connected to the gear shaft 63 and engaged with a worm gear disk 641 on a cam 64. An arm 65 is pivotally connected to the cam 64 and clamps a main shaft 66 so that when the cam 64 is rotated, the main shaft 66 is moved up and down to activate a knife changing device. A main shortcoming is that the distance from the gear shaft 63 to the cam 64 is so long that a large scale of cam 64 is required which is costly and heavy. An unexpected gap is found between the gear shaft 63 and the cam 64 after being used for a period of time, this gap will result in a huge wear between the gear shaft 63 and the worm gear disk 641. Not only noise is generated but the precision of the knife changing is reduced, and this could make knife drop happen. Furthermore, the main shaft 66 is movably mounted to a hexagonal post 67, and the precision between the main shaft 66 and the hexagonal post 67 is obtained by a costly price.
The present invention intends to provide a transmission device for knife changing mechanism wherein the distance between the control shaft and the cam is shortened.
In accordance with one aspect of the present invention, there is provided a transmission device for knife changing mechanism of a machine center and comprising a motor connected to a top of a casing and driving an output shaft on which a first bevel gear is connected to the output shaft and engaged with a second bevel gear mounted to a cam shaft on which a cam disk is mounted. A first groove is defined in a first side of the cam disk and a second groove is defined in a second side of the cam disk. A rack has a first pin movably engaged with the first groove and an arm having a first end pivotally connected to the casing and a pin extends from the arm and movably engaged with the second groove. A main shaft movably extends through the top of the casing and has a toothed section and an annular groove is defined in an outer periphery of the main shaft. A second end of the arm is engaged with the annular groove. A tube is connected to the top of the casing and the main shaft is movably inserted in the tube. A first detection device and a second detection device are respectively and radially connected to the tube. A control shaft extends through an aperture defined through the top of the casing and is fixedly connected to a cap on the top of the casing. A first idle gear and a second idle gear are respectively mounted to the control shaft. The first idle gear is engaged with the rack and the second idle gear is engaged with the toothed section on the main shaft.
The primary object of the present invention is to provide a transmission device for knife changing mechanism and the device has a compact size and the distance between the control shaft and the cam is shortened.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.